add url slug resolution to shop routing

Shop.Page resolves custom URLs to correct page types:
- resolve_custom_slug/2 detects system pages with custom URLs
- Dynamic prefix resolution for /:prefix/:id routes
- Updates live_action when slug resolves to different type

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/berrypod_web/live/shop/page.ex

@@ -9,10 +9,11 @@ defmodule BerrypodWeb.Shop.Page do
   use BerrypodWeb, :live_view
 
   alias BerrypodWeb.Shop.Pages
+  alias BerrypodWeb.R
   alias Berrypod.{Media, Settings}
   alias Berrypod.Workers.FaviconGeneratorWorker
 
-  # Map live_action atoms to page handler modules
+  # Map page type atoms to handler modules
   @page_modules %{
     home: Pages.Home,
     product: Pages.Product,
@@ -187,10 +188,22 @@ defmodule BerrypodWeb.Shop.Page do
     action = socket.assigns.live_action
     prev_action = socket.assigns[:_current_page_action]
     prev_path = socket.assigns[:_current_path]
-    module = @page_modules[action]
     parsed_uri = URI.parse(uri)
     current_path = parsed_uri.path
 
+    # For custom_page action, check if slug is a custom URL for a system page
+    {action, params} = resolve_custom_slug(action, params)
+
+    # Update live_action if we resolved to a different page type
+    socket =
+      if action != socket.assigns.live_action do
+        assign(socket, :live_action, action)
+      else
+        socket
+      end
+
+    module = @page_modules[action]
+
     # Clean up previous page if needed (e.g., unsubscribe from PubSub)
     socket = maybe_cleanup_previous_page(socket, prev_action)
 
@@ -375,4 +388,51 @@ defmodule BerrypodWeb.Shop.Page do
   end
 
   defp clear_page_specific_assigns(socket, _), do: socket
+
+  # Resolve custom URL slugs to system pages
+  # E.g., if cart page has url_slug: "basket", visiting /basket should load the cart page
+  defp resolve_custom_slug(:custom_page, %{"slug" => slug} = params) do
+    case R.page_type_from_slug(slug) do
+      {:page, page_type} ->
+        # Custom URL for a system page - dispatch to that page type
+        # Preserve other params (like query params) but remove slug
+        {page_type, Map.delete(params, "slug")}
+
+      {:custom, _page} ->
+        # Regular custom CMS page - let CustomPage handle it
+        {:custom_page, params}
+
+      nil ->
+        # Unknown slug - let CustomPage handle the 404
+        {:custom_page, params}
+    end
+  end
+
+  # Handle dynamic prefix routes for products, collections, and orders.
+  # Works with both default prefixes (/products/123) and custom prefixes (/p/123).
+  # R.prefix_type_from_segment checks both the ETS cache (custom) and defaults.
+  defp resolve_custom_slug(:dynamic_prefix, %{"prefix" => prefix} = params) do
+    # The second segment param name is "id_or_slug" from the route definition
+    id_or_slug = params["id_or_slug"]
+    # Preserve query params by keeping all params except route-specific ones
+    other_params = Map.drop(params, ["prefix", "id_or_slug"])
+
+    case R.prefix_type_from_segment(prefix) do
+      :collections ->
+        {:collection, Map.put(other_params, "slug", id_or_slug)}
+
+      :products ->
+        {:product, Map.put(other_params, "id", id_or_slug)}
+
+      :orders ->
+        {:order_detail, Map.put(other_params, "order_number", id_or_slug)}
+
+      nil ->
+        # Not a known prefix - check if combined path is a system page (e.g. checkout/success)
+        combined_slug = prefix <> "/" <> id_or_slug
+        resolve_custom_slug(:custom_page, Map.put(other_params, "slug", combined_slug))
+    end
+  end
+
+  defp resolve_custom_slug(action, params), do: {action, params}
 end